dbus-launch --exit-with-session and stdin

[Havoc Pennington]

Artem Kachitchkine wrote:
> The babysitter process does appear to stay attached to the original tty 
> and would kill_bus_and_exit() when SIGHUP is received. But then there's 
> this additional code:
> 
>           if (FD_ISSET (tty_fd, &read_set))
>             {
>               int bytes_read;
>               char discard[512];
> 
>               verbose ("TTY ready for reading\n");
> 
>               bytes_read = read (tty_fd, discard, sizeof (discard));
> 
>               verbose ("Read %d bytes from TTY errno = %d\n",
>                        bytes_read, errno);
> 
>               if (bytes_read == 0)
>                 kill_bus_and_exit (); /* EOF */
> 
> What is it supposed to do that SIGHUP wouldn't do?

I don't honestly remember the history of this code. What the above does 
(to state the obvious) is exit if stdin gets EOF, but I don't know why. 
Conceivably we rely on it somewhere by starting a bus with a pipe on 
stdin or something instead of a tty.

> This code giving us a problem on Solaris: we start session bus from 
> Xinitrc in an obvious way:
> 
> command=/usr/bin/gnome-session
> if [ -x "/usr/bin/dbus-launch" -a -z "$DBUS_SESSION_BUS_ADDRESS" ]; then
>     command="/usr/bin/dbus-launch --exit-with-session $command"
> fi
> exec $command
> 
> but the first read() returns 0 (still need to figure out why), so the 
> session bus is killed immediately, even though the session runs normally.

is stdin a tty, or perhaps /dev/null or the like that would give an EOF 
instead of a HUP?

I don't know if the dbus code tests isatty()

Havoc